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Coral Anatomy |
Cnidarians have relatively simple body structures. This is as compared to more complex animals, such as humans. A cnidarian’s body is made up of only two epithelia, which are cell layers. The two epithelial cell layers are the outer ectoderm and inner gastroderm. You can find the zooxanthellae located in the inner gastroderm layer. Each epithelia is composed of solely one layer of cells. These two body layers are separated by non-cellular jelly called the mesoglea. Corals may only have two cell layers, but that certainly does not mean they are limited to only two cell types. The types of cells that coral’s have include nerve cells, sensorial cells, muscular cells, reproductive cells, and nematocysts. The nematocysts are noteworthy because they are used sting, catch, and kill prey bigger than itself.
See: structure of coral cell layer
The Body Geometry
The closest relative to coral polyps are sea anemones. They are similar to corals in
their body structure and overall appearance. Cnidarians have two possible body sha
pes: polyp and jellyfish. Both of them have
single mouth. Corals appear only in the polyp form. The basic geometry of the polyp form
is a cylinder. The cylinder is closed by an oral disk from above. Located in the center of
the oral disc is a mouth, which is encircled by tentacles. The polyp’s cylinder is
closed from below by a basal disk. The basal disk fixes the polyp to substrate.
The drawing on right shows structure of polyp body:
1. colenteron
2. mouth
3. tentacle
4. oral disk
5. basal disk
You can also see:
The coral polyp is essentially a contractile sac. On the mouth are a multiple of 6 tentacles armed with stinging nematocysts. More clearly, a nematocyst is an arrow-like barb filled with toxins that are able to sting microscopic crustaceans and other small organisms. It is important to note that coral nematocysts are not powerful enough to harm humans. They pose absolutely no threat to humans. As mentioned before, coral sizes can range from as tiny as 1 mm to over 1 m across in diameter.
Since the mouth is the only opening in the polyp, it also serves also as an anus where waste products are disposed. Following along the coral mouth will first lead to pharynx. Next follows the coelenteron. Both the mouth and pharynx are covered by the ectoderm. The coelenteron, on the otherhand, is covered by the gastroderm. The coelenteron is divided into parts by mesenteries. You can a imagine mesenteries streaming down from the oral disc just as a set curtains would.
